Banjo



Nov. 15, 1927.

F. J. BACON BANJO Filed April 1922 Patented Nov. 15, 1927.

UNITED STATES FREDERICK J. BAGGN, 9F NEW LONDON, CONNECTICUT.

BANJO.

Application filed'lipril 18, 1922. Serial No. 554,922.

This invention relates to improvements in stringed musical instruments and more particularly to an improvement in the resonance boxes of banjos, although the invention. is not restricted to this particular type of stringed musical instruments.

The resonance box of the ordinary banjo is open at its back and as a consequence the sound waves are directed against the clothing of the player of the instrument and are somewhat deadened or muffled thus greatly detracting from the quality of the tone. Therefore it is the primary object of the present invention to overcome this difliculty and to provide means whereby the resonance of the instrument will be greatly increased and the quality of the tones greatly improved. In this connection also the inventionhas as its object to so construct the resonance box of the instrument that the tones will be materially amplified as well. as improved in quality. In attaining these ob.- jects the invention has as its object the provision of a resonant back for the resonance 302; of the instrument which back will possess certain features of design and construction rendering it highly responsive to sound wave vibrations and adapting it to serve effectually as a mediumfor amplifying the sound waves and improving the tonal qualities.

By. providing means for amplifying the sound waves delivered from the resonance box of the instrument, I especially adapt the instrument for concert use but as it may at times be desirable to render music in a more or less subdued tone, I contemplate arrangement of the resonant back of the resonance box within the open side of the box in such manner as to permit of its ready removal for this purpose.

Not only does .the present invention have as its object the provision within the usuall open back of the resonance box of a resonance sound wave amplifying medium which will respond to the sound wave vibrations and amplify the tones, but it also resides in so forming the wall of the box as to most effectually distribute and deliver the sound waves.

Another objectof the invention is to so form the circumferential wall of the resonance box as to further enhance the quality ofthe tones and render this wall responsive to the sound wave vibrations and at the same time increase the responsiveness of the membranous head of the resonance box to these vibrations.

In the accompanying drawings:

Figure lis a perspective view of a banjo constructed in accordance with the present invention; and V f Figure 2 is a diametric sectional view through the resonance box thereof substantially on the line 2-2 of Figure 1 looking in thedirection indicated by the arrows.

In the drawings the resonance box of the instrument is indicated in general by the nu meral l and the neck of the instrument by the numeral 2, the latter being of the ordinary construction and connected in the usual manner with the resonance box. Aspreviously stated the invention is not restricted to embodiment in a banjo, for the principles thereof may equally as well find embodiment in other stringed musical instruments of a similar nature. i

The resonance box 1 in theconstruction of which the invention primarily resides, comprises, as is usuaha circumferential wall indicated by the numeral 3 and which wall may bemade of any material found s'uitable for the purpose and is of the usual annular form. However this wall is, in its cross sectional dimensions, decreased in thickness from the back to the'front of the resonance boX as clearlyshown in FigureQ. This reduction in thickness may be effected by forming the rear portion of the wall of substantially uniform thickness as indicated by the nruneral i, and the forward portion of the wallgradually thinned as indicated bythe numeral 5, and preferably by beveling or flaring the inner surface of this portion of the wall, the outer surface of the wall retaining its usual cylindrical contour. The ad 'antage obtained by forming-the wall 3 of the resonance box of decreasing; thickness in the direction of the forward side of the box is that in this manner the respon siveness of the wall tosound wave vibra tions is materially increased and the quality of the tones is enhanced. This construction also presents a'further advantage which will presently be'pointed out.

The membranous head of the resonance box is indicated by the numeral 6 ancl'the same comprises the usual calfskin membrane which is stretched at its marginal portion over the thinner front edge of the wall 3 of the box and suitably tensioned by a tensioning ring 7 applied about its said portion and adapted to be drawn inwardly by the usual tensioning clamps 8 arranged at suitable intervals about the circumference of the wall 3. Preferably the outer surface of the wall 3 is rabbeted or countersunk as at I) so as to accomn'iodate a metallic band ll) which is disposed about the thinner forward portion of the wall and has its forward edge portion overturned in an inward direction or flanged as indicated by the numeral 11, the flange 11 being relatively narrow and engaging over the thin forward edge of said wall 3. Because of the reduced thickness of the wall. 3 at its forward ed e, the calfskin head 6 when stretched over this edge of the wall will poi a greater degree of responsiveness to the sound wave vibrations than if this edge of the wall. were relatively thick, and this the additional advantage referred to above as presented by the reduction in thickness of the wall in the direction of the forward side of the box. It will also be evident that the provision of the flange 1.1 presents the advantage that by extending over the thin edge of the wall 3, splintering of this edge when the wall is n'iade of wood, is effectually prevented.

The resonant sound amplifying medium which chiefly constitutes the present inven-- tion, is indicated in general by the numeral 12 and the same comprises a circular head 13 preferably of wood, although other resonant material may be employed for the purpose, and of a marginal contour and dimensions to adapt it to be fitted into the back of the sound box 1 which back is ordinarily left open in instruments of this type. Generally speaking the head 13 is of concavo-conveX form, being concave upon its inner surface and convex upon its outer surface, and preferably the head at its middle portion 14- is of ininirnun'i thickness and is gradually increased in thickness as at 15 toward the periphery of the head. This peripheral portion which is indicated by the numeral 16 is relatively thick so that the head will be sufficiently substantial to adapt it to be lirmly fitted into the open back of the resonance box and also removed there from when desired without likelihood of distortion or injury. In order to adapt the head to be firmly frictionall fitted and held. within the said open back of the box, a strip 17 of felt or other suitable material is secured by tacks or otherwise to the peripheral surface of the portion lti of the head and the strip is then folded back upon itself as indicated by the numeral 18 and its other edge portion 19 is brought over the inner face of the peripheral portion 16 of the head and preferably united thereto by adhesive or any other agent. By reason of the nature of the material of which the strip 17 is made, it provides a yielding marginal friction alby means for obtaining a snug and firm lit of the member 12 within the open back of the resonance box and yet it permits of ready removal of the said member when this desired. In order that the member 12 may be readily placed in position and removed as occasion requires, finger knobs 20 are preferably secu upon the back or outer side of the head 13 near the periphery thereof and at diametrically opposite points.

From the foregoing it will be evident that the head 13 will be highly responsive to the sound waves propagated through vibration of the strings of the instrument and that these Waves will be greatly amplified by reason of the resonant quality of the head, and in order to properly distribute the an'iplitierl waves in. all directions and increase the quality of the tones, the wall 3 of the resonance her: is preferably formed at intervals in its circumference with sound openings 21, these openings being preferably located in the portion of said wall, and the band 10 being formed with similar openings 22 which register therewith.

lVhere the term front, or a similar term, is employed in this specification and in the claims, it is intended to designate the side of the body or resonance box to which the ineniliranoui-s head is secured, while the term back, or the like, refers to that side of the resonance box or body which is open in haw jos of ordinary construction.

Having thus described the invention, what is claimed as new is:

1. The combination with a stringed musical instrument of the type having a. resonance box theback of which is ordinarily open, of an amplifier attachment therefor comprising a resonant sound amplifying head removahly fitted within said back, the head being of minimum thickness at its central. portion and of gradually increasing thickness in the direction of its )eri ')hery, and a friction element of yieldable material covering the entire periphery of said head and in frictional contact with the inner side of the wall of the resonance box.

2. A stringed musical instrument having a, resonance box comprising a circnmferem tial wall thinned in the direction of one side of the box, a metallic band surrounding said wall and having a flange extending around the upper edge and engaging over the thinner edge of the wall, a men'ibranmis head stretched over the flange, and means on the wall for marginally engaging said head and securing the same.

3. A strin ed musical instrument including resonance box comprising a circumferential wall, a resonant sound amplifying head fitted into the back of the resonance box and having frictional contact throughout its entire periphery with the wall whereto be removably held, the said wall of the box being decreased in thickness from its back to its front whereby the wall at the front of the box is relatively thin, and a membranous head stretched directly over and in contact with said thinner edge of the said wall, the thinned portion of the wall being provided with a circumferential series of radial openings therethrough.

4. An amplifying attachment for stringed musical instruments of the type having a resonance box the back of which is ordinari- 1y open the sald attachment comprismg a resonant sound amplifying head of minimum thickness at its central portion and 0t gradually increasing thickness in the direction of its periphery and having its said periphery cylindrical, and a friction band secured to the periphery of the head and extending continuously about the same and constituting means for trictionally removably holding the head entirely Within the back of the resonance box of the instrument.

In testimony whereof I alfix my signature.

FREDERICK J. BACON. [11. s] 

